Combustor liner cooling system

ABSTRACT

A turbine engine with a combustor that includes a hollow wall about a combustor liner. The combustor liner includes an inner surface facing inwardly toward a combustion chamber. The turbine engine includes a first air flow path in an upstream direction through the hollow wall toward a head end of the combustor. The first air flow path includes a plurality of bypass openings extending through the combustor liner to the inner surface to supply a first cooling film to a downstream end portion of the combustor liner. The turbine engine further includes a second flow path in a second direction opposite the upstream direction through the hollow wall. The second flow path includes a plurality of film holes extending through the combustor liner to the inner surface to supply a second cooling film to the downstream end portion of the combustor liner downstream of the first cooling film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/401,530, entitled “COMBUSTOR LINER COOLING SYSTEM”, filed Mar. 10,2009, which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to gas turbine engines and,more specifically, to a system for cooling a combustor liner used in acombustor of a gas turbine engine.

Gas turbine engines typically include a combustor having a combustorliner defining a combustion chamber. Within the combustion chamber, amixture of compressed air and fuel is combusted to produce hotcombustion gases. The combustion gases may flow through the combustionchamber to one or more turbine stages to generate power for driving aload and/or a compressor. Typically, the combustion process heats thecombustor liner due to the hot combustion gases. Unfortunately, existingcooling systems may not adequately cool the combustor liner in allconditions.

BRIEF DESCRIPTION OF THE INVENTION

Certain embodiments commensurate in scope with the originally claimedinvention are summarized below. These embodiments are not intended tolimit the scope of the claimed invention, but rather these embodimentsare intended only to provide a brief summary of possible forms of theinvention. Indeed, the invention may encompass a variety of forms thatmay be similar to or different from the embodiments set forth below.

In one embodiment, a system includes a turbine engine. The turbineengine includes a combustor that includes a hollow wall about acombustor liner. The combustor liner includes an inner surface facinginwardly toward a combustion chamber. The turbine engine also includes afirst air flow path in an upstream direction through the hollow walltoward a head end of the combustor. The first air flow path includes aplurality of bypass openings extending through the combustor liner tothe inner surface to supply a first cooling film to a downstream endportion of the combustor liner. The turbine engine further includes asecond flow path in a second direction that is opposite the upstreamdirection through the hollow wall. The second flow path may include aplurality of film holes extending through the combustor liner to theinner surface to supply a second cooling film to the downstream endportion of the combustor liner downstream of the first cooling film.

In another embodiment, a system includes a turbine combustor liner. Theturbine combustor liner includes a plurality of axial cooling channelsarranged circumferentially about a downstream end portion of the turbinecombustor liner, the downstream end portion being relative to adownstream direction of combustion along a longitudinal axis of theturbine combustor liner. The turbine combustor includes an inner surfacefacing inwardly toward a combustion chamber, and a plurality of bypassopenings arranged circumferentially about the downstream end portionupstream of the plurality of axial cooling channels. The plurality ofbypass openings is configured to supply a first cooling film to theinner surface of the combustion liner, and each of the plurality ofaxial cooling channels includes one or more film holes configured tosupply a second cooling film to the inner surface of the combustor linerat the downstream end portion.

In yet another embodiment, a system includes a turbine engine having acombustor with a flow sleeve and a combustor liner surrounded by theflow sleeve. The combustor liner and flow sleeve define a flow paththerebetween configured to receive an air flow in a first directiontowards a head end chamber. The combustor liner includes an innersurface facing inwardly toward a combustion chamber, a plurality ofaxial cooling channels arranged circumferentially about a downstream endportion of the combustor liner, a plurality of bypass holes arranged intwo or more axially spaced sets at the downstream end portion, and oneor more fuel nozzles disposed in the head end chamber of the combustor.Each bypass opening is disposed upstream in the first direction relativeto an axial cooling channel of the plurality of axial cooling channels.Each bypass opening is configured to supply a first cooling film to theinner surface of the combustor liner at the downstream end portion. Eachof the plurality of axial cooling channels includes a plurality of filmholes extending through the combustor liner to the inner surface. Eachof the plurality of axial cooling channels is configured to receive aportion of the air flow from the flow path, to direct a first portion ofthe received air along an axial length of the axial cooling channel in asecond direction away from the head end chamber, and to direct a secondportion of the received air through the plurality of film holes tosupply a second cooling film to the inner surface of the combustor linerat the downstream end portion.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a block diagram of a turbine system having a combustor linerhaving cooling channels for enhanced cooling, in accordance with anembodiment of the present technique;

FIG. 2 is a cutaway side view of the turbine system, as shown in FIG. 1,in accordance with an embodiment of the present technique;

FIG. 3 is a cutaway side view of the combustor, as shown in FIG. 1,having a combustor liner with cooling channels at a downstream endportion, in accordance with an embodiment of the present technique;

FIG. 4 is an exploded perspective view of certain components of thecombustor, as shown in FIG. 3, in accordance with an embodiment of thepresent technique.

FIG. 5 is a partial perspective view of a portion of the coolingchannels on the downstream end portion of the combustor liner, takenwithin line 5-5 as shown in FIG. 4, in accordance with an embodiment ofthe present technique;

FIG. 6 is a partial cross-sectional side view of the downstream endportion of the combustor liner, taken within line 6-6 as shown in FIG.3, in accordance with an embodiment of the present technique;

FIGS. 7A and 7B are partial cross-sectional end views of a coolingchannel within the downstream end portion of the combustor liner, takenalong line 7-7 as shown in FIG. 6, in accordance with embodiments of thepresent technique;

FIGS. 8A-8D are partial cross-sectional side views illustratingconfigurations of holes within a cooling channel of the downstream endportion of the combustor liner, taken within line 8-8 as shown in FIG.6, in accordance with embodiments of the present technique; and

FIG. 9 is a partial cross-sectional side view of the downstream endportion of the combustor liner, taken within line 6-6 as shown in FIG.3, in accordance with a further embodiment of the present technique.

DETAILED DESCRIPTION OF THE INVENTION

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, all features of an actual implementation may not bedescribed in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering ordesign project, numerous implementation-specific decisions must be madeto achieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

When introducing elements of various embodiments of the presentinvention, the articles “a,” “an,” “the,” and “said” are intended tomean that there are one or more of the elements. The terms “comprising,”“including,” and “having” are intended to be inclusive and mean thatthere may be additional elements other than the listed elements. Anyexamples of operating parameters and/or environmental conditions are notexclusive of other parameters/conditions of the disclosed embodiments.Additionally, it should be understood that references to “oneembodiment” or “an embodiment” of the present invention are not intendedto be interpreted as excluding the existence of additional embodimentsthat also incorporate the recited features.

Before continuing, several terms used extensively throughout the presentdisclosure will be first defined in order to provide a betterunderstanding of the claimed subject matter. As used herein, the terms“upstream” and “downstream,” when discussed in conjunction with acombustor liner, shall be understood to mean the proximal end of thecombustor liner and the distal end of the combustor liner, respectively,with respect to the fuel nozzles. That is, unless otherwise indicated,the terms “upstream” and “downstream” are generally used with respect tothe flow of combustion gases inside the combustor liner. For example, a“downstream” direction refers to the direction in which a fuel-airmixture combusts and flows from the fuel nozzles towards a turbine andan “upstream” direction refers to a direction opposite the downstreamdirection, as defined above. Additionally, the term “downstream endportion,” “coupling portion,” or the like, shall be understood to referto an aft-most (downstream most) portion of the combustor liner. As willbe discussed further below, the axial length of the downstream endportion of the combustor liner, in certain embodiments, may be as muchas approximately 20 percent the total axial length of the combustorliner. The downstream end portion (or coupling portion), in someembodiments, may also be understood to be the portion of the liner thatis generally configured to couple to a downstream transition piece ofthe combustor, generally in a telescoping, concentric, or coaxialoverlapping annular relationship. Further, where the term “liner”appears alone, it should be understood that this term is generallysynonymous with “combustor liner.”

Keeping in mind the above-defined terms, the present disclosure isgenerally directed towards a combustor liner capable of providing moreeffective cooling during the operation of a turbine engine. In oneembodiment, the liner has a downstream end portion that includes aplurality of channels (also referred to herein as “cooling channels”)arranged circumferentially about the outer surface of the downstream endportion. The channels may define a flow path that is parallel to thelongitudinal axis of the liner. Further, each channel may each includeone or more openings that fluidly couple the channel to the combustionchamber. While certain embodiments will refer to these openings as “filmholes,” it should be understood that the openings may include holes,slots, or a combination of holes and slots, and may be formed using anysuitable technique, such as laser drilling, for example.

In operation, an annular wrapper having a plurality of openingsextending radially therethrough may be coupled to the liner generallyabout the downstream end portion. The inner surface of the wrapper andthe cooling channels on the downstream end portion may define one ormore passages through which an air flow may be supplied via one or moreopenings on the wrapper. The air flow may be a portion of the compressedair supplied to the combustor for combustion of fuel. As the air flowsthrough a cooling channel, heat may be transferred away from thecombustor liner, particularly the downstream end portion of the liner,via forced air convention. Additionally, a portion of the air flowwithin the cooling channel may flow through the film holes and into thecombustion chamber to provide a film of cooling air which insulates theliner, particularly the downstream end portion of the liner, from therelatively hotter combustion gases within the combustor, thereby coolingthe liner via film cooling.

In some embodiments, the liner may further include a plurality of“bypass openings” in addition to the film holes discussed above. Thebypass openings may be located upstream from the cooling channels andmay extend radially through the combustor liner. The bypass openings mayprovide a direct flow path into the combustion chamber (e.g., interiorof the combustor liner) that bypasses the cooling channels discussedabove. Air may flow into the combustion chamber along this path, thusproviding an additional cooling film along the interior of the surfaceof the combustor liner upstream from the cooling film provided via thefilm holes, thereby further insulating the liner from combustion gaseswithin the liner. In this manner, embodiments of the present inventionmay provide for enhanced heat transfer using forced convection and filmcooling principles simultaneously. Advantageously, this may improveoverall turbine performance and increase the life of the combustorand/or combustor liner.

Turning now to the drawings and referring first to FIG. 1, a blockdiagram of an embodiment of a turbine system 10 is illustrated. Asdiscussed in detail below, the disclosed turbine system 10 may employ acombustor liner having cooling channels formed on a downstream endportion of the liner. The cooling channels may include film holes thatprovide for improved cooling of the downstream end portion, as will bediscussed further below. The turbine system 10 may use liquid or gasfuel, such as natural gas and/or a hydrogen rich synthetic gas, to runthe turbine system 10. As depicted, a plurality of fuel nozzles 12intakes a fuel supply 14, mixes the fuel with air, and distributes theair-fuel mixture into a combustor 16. The air-fuel mixture combusts in achamber within combustor 16, thereby creating hot pressurized exhaustgases. The combustor 16 directs the exhaust gases through a turbine 18toward an exhaust outlet 20. As the exhaust gases pass through theturbine 18, the gases force one or more turbine blades to rotate a shaft22 along an axis of the system 10. As illustrated, the shaft 22 may beconnected to various components of turbine system 10, including acompressor 24. The compressor 24 also includes blades that may becoupled to the shaft 22. As the shaft 22 rotates, the blades within thecompressor 24 also rotate, thereby compressing air from an air intake 26through the compressor 24 and into the fuel nozzles 12 and/or combustor16. The shaft 22 may also be connected to a load 28, which may be avehicle or a stationary load, such as an electrical generator in a powerplant or a propeller on an aircraft, for example. As will be understood,the load 28 may include any suitable device that capable of beingpowered by the rotational output of turbine system 10.

FIG. 2 illustrates a cutaway side view of an embodiment of the turbinesystem 10 schematically depicted in FIG. 1. The turbine system 10includes one or more fuel nozzles 12 located inside one or morecombustors 16. The combustor 16 may include one or more combustor linersdisposed within one or more respective flow sleeves. As mentioned above,the combustor liner (or liners) may include a plurality of coolingchannels formed on a downstream end portion of the liner. Each coolingchannel may also include openings, such as film holes, which fluidlycouple the cooling channel to the combustion chamber defined by theliner.

In operation, air enters the turbine system 10 through the air intake 26and may be pressurized in the compressor 24. The compressed air may thenbe mixed with gas for combustion within combustor 16. For example, thefuel nozzles 12 may inject a fuel-air mixture into the combustor 16 in asuitable ratio for optimal combustion, emissions, fuel consumption, andpower output. The combustion generates hot pressurized exhaust gases,which then drive one or more blades 17 within the turbine 18 to rotatethe shaft 22 and, thus, the compressor 24 and the load 28. The rotationof the turbine blades 17 causes a rotation of shaft the 22, therebycausing blades 19 within the compressor 22 to draw in and pressurize theair received by the intake 26.

As will be discussed in further detail below, each of the coolingchannels on the downstream end portion of the combustor liner mayreceive a portion of the air supplied to the combustor 16 through theair intake 26. In one embodiment, the total air supplied to the coolingchannels may make up approximately 2% of the total air supplied to thecombustor 16 via compressor 24 and intake 26. As the compressor-suppliedair (which is generally substantially cooler relative to the combustiongases within the combustor 16) flows through the cooling channels, heatis transferred away from the downstream end portion of the liner (e.g.,via forced convection cooling). Further, a portion of the airflow withineach cooling channels may flow through the film holes and form a coolingfilm along a portion of the inner surface of the liner. The cooling filminsulates the liner from the relatively hot combustion gases flowingwithin the combustor 16. Thus, in operation, cooling of the liner,particularly the downstream end portion of the liner, is enhanced byutilizing both forced convection and film cooling techniques.

Continuing now to FIG. 3, a more detailed cutaway side view of anembodiment of the combustor 16, as shown FIG. 2, is illustrated. As willbe appreciated, the combustor 16 is generally fluidly coupled to thecompressor 24 and the turbine 18. The compressor 24 may include adiffuser 29 and a discharge plenum 31 that are coupled to each other influid communication as to facilitate the channeling of air downstream tothe combustor 16. In the illustrated embodiment, the combustor 16includes a cover plate 30 at the upstream head end of the combustor 16.The cover plate 30 may at least partially support the fuel nozzles 12and provide a path through which air and fuel are directed to the fuelnozzles 12.

The illustrated combustor 16 comprises a hollow annular wall configuredto facilitate cooling air flow. For example, the combustor 16 includes acombustor liner 34 disposed within a flow sleeve 32. The arrangement ofthe liner 34 and the flow sleeve 32, as shown in FIG. 3, is generallyconcentric and may define an annular passage 36. In certain embodiments,the flow sleeve 32 and the liner 34 may define a first or upstreamhollow annular wall of the combustor 16. The interior of the liner 34may define a substantially cylindrical or annular combustion chamber 38.The flow sleeve 32 may include a plurality of inlets 40, which provide aflow path for at least a portion of the air from the compressor 24 intothe annular passage 36. In other words, the flow sleeve 32 may beperforated with a pattern of openings to define a perforated annularwall.

Downstream from the liner 34 and the flow sleeve 32 (e.g. in thedirection 39), a second flow sleeve 42, which may be referred to as an“impingement sleeve,” may be coupled to the flow sleeve 32. Thus, thedirection 39 may represent a downstream direction with respect to theflow of combustion gases away from the fuel nozzles 12 inside the liner34. As used herein, the terms “upstream” and “downstream,” whendiscussed in conjunction with a combustor liner, shall be understood tomean the proximal end of the combustor liner and the distal end of thecombustor liner 34, respectively, with respect to the fuel nozzles 12.That is, unless otherwise indicated, the terms “upstream” and“downstream” are generally used with respect to the flow of combustiongases inside the combustor liner. For example, a “downstream” directionrefers to the direction 39 in which a fuel-air mixture combusts andflows from the fuel nozzles 12 towards the turbine 18, and an “upstream”direction refers to a direction opposite the downstream direction, asdefined above.

In the present embodiment, the flow sleeve 32 may include a mountingflange 44 configured to receive a portion of the impingement sleeve 42.A transition piece 46 (which may be referred to as a “transition duct”)may be disposed within the impingement sleeve 42. A concentricarrangement of the impingement sleeve 42 and the transition piece 46 maydefine an annular passage 47. As shown, the annular passage 47 isfluidly coupled to the annular passage 36. In certain embodiments, thesleeve 42 and the transition piece 46 may define a second or downstreamhollow annular wall of the combustor 16. Thus, together, the elements32, 34, 42, and 46 define a hollow annular wall (e.g., upstream anddownstream portions) configured to facilitate air flow to the fuelnozzles 12, while also cooling the combustor 16 due to the heatgenerated from combustion.

The impingement sleeve 42 may include a plurality of inlets 48 (e.g.,perforated annular wall), which may provide a flow path for at least aportion of the air from the compressor 24 into the annular passage 47.An interior cavity 50 of the transition piece 46 generally provides apath by which combustion gases from the combustion chamber 38 may bedirected thru a turbine nozzle 60 and into the turbine 18. In thedepicted embodiment, the transition piece 46 may be coupled to thedownstream end of the liner 34 (with respect to direction 39), generallyabout a downstream end portion 52 (coupling portion), as discussedabove. An annular wrapper 54 and a seal may be disposed between thedownstream end portion 52 and the transition piece 46. The seal maysecure the outer surface of the wrapper 54 to inner surface of thetransition piece 46. Further, as mentioned above, the inner surface ofthe wrapper 54 and the cooling channels on the downstream end portionmay define passages that receive a portion of the air flow from theannular passage 47.

As discussed above, the turbine system 10, in operation, may intake airthrough the air intake 26. The compressor 24, which is driven by theshaft 22, rotates and compresses the air. The compressed air isdischarged into the diffuser 29, as indicated by the arrows shown inFIG. 3. The majority of the compressed air is further discharged fromthe compressor 24, by way of the diffuser 29, through a plenum 31 intothe combustor 16. Though not shown in detail here, a smaller portion ofthe compressed air may be channeled downstream for cooling of othercomponents of the turbine engine 10. A portion of the compressed airwithin the plenum 31 may enter the annular passage 47 by way of theinlets 48. The air in the annular passage 47 is then channeled upstream(e.g., in the direction of fuel nozzles 12) towards the annular passage36, such that the air flows over the downstream end portion 52 of theliner 34. That is, a flow path in the upstream direction (relative todirection 39) is defined by the annular passages 36 (formed by sleeve 32and liner 34) and 47 (formed by sleeve 42 and transition piece 46). Aportion of the air flowing in the upstream direction is diverted intothe cooling channels on the downstream end portion of the liner 34 tofacilitate cooling. In one embodiment, a plurality of inlets on thewrapper 54 may provide a flow path into the cooling channels. Asmentioned above, air flowing through the channel may cool the liner 34via forced convection cooling. Additionally, a portion of the airflowwithin the channel may be diverted through one or more film holes withinthe channel and into the combustion chamber 38, as indicated by the airflow 53. The air flow 53 may form a cooling film that insulates thedownstream end portion 52 of the liner 34 from the hot combustion gaseswithin the chamber 38.

The portion of the air flow that is not discharged into the coolingchannel continues to flow upstream into the annular passage 36 towardthe cover plate 30 and fuel nozzles 12. Accordingly, the annular passage36 may receive air from the annular passage 47 and the inlets 40. Asshown in FIG. 3, a portion of the air flow within the annular passage 36may be directed into one or more bypass openings 41 on the liner 34. Thebypass openings 41 extend radially through the liner 34 and provide adirect flow path into the combustion chamber 38 that bypasses thecooling channels on the downstream end portion 52. The air 43 that flowsinto the combustion chamber 38 through the bypass openings 41 mayprovide an additional cooling film along the inner surface of the liner34 upstream from the cooling film provide via film holes within thecooling channels, thus providing additional insulation for the liner 34.The remaining air flowing into the annular passage 36 is then channeledupstream towards the fuel nozzles 12, wherein the air is mixed with fuel14 and ignited within the combustion chamber 38. The resultingcombustion gases are channeled from the chamber 38 into the transitionpiece cavity 50 and through the turbine nozzle 60 to the turbine 18.

FIG. 4 is an exploded perspective view showing some of theabove-discussed components of the combustor 16. Particularly, FIG. 4 isintended to provide a better understanding of the relationship betweenthe liner 34, the wrapper 54, and the transition piece 46. As shown, theliner 34 may have a length of L1 when measured along a longitudinalaxis, referred to here by reference number 58. In the illustratedembodiment, a radius R1 of the upstream end of the liner 34 may begreater than a radius R2 of the downstream end of the liner 34. In otherembodiments, however, the radii R1 and R2 may be equal or the radius R2may be greater than the radius R1. The liner 34 includes the downstreamend portion 52. As discussed above, the downstream end portion 52 is aportion of the liner having an axial length L2 which, when measured fromthe downstream (aft-most) end of the liner 34, is less than the totallength L1 of the liner 34. In one embodiment, the length L2 of thedownstream end portion 52 may be approximately 10-20 percent of thetotal length L1 of the liner. However, it should be appreciated that inother embodiments, depending on implementation specific goals, thelength L2 could be greater than 20 percent or less than 10 percent ofL1. For example, in other embodiments, the longitudinal length L2 of thedownstream end portion 52 may be at least less than approximately 5, 10,15, 20, 25, 30, or 35 percent of the total length L1.

The wrapper 54 is configured to mate with the liner 34 generally aboutthe downstream end portion 52 in a telescoping, coaxial, or concentricoverlapping relationship. The transition piece 46 is coupled to theliner 34 generally about the downstream end portion 52 and the wrapper54. A sealing ring 66 may be disposed between the wrapper 54 and thetransition piece 46 to facilitate the coupling. As shown, the wrapper 54may include a plurality of inlets 68 generally near the upstream end ofthe wrapper 54. In the illustrated embodiment, the inlets 68 aredepicted as a plurality of openings disposed circumferentially (relativeto the axis 58) about the upstream end of the wrapper 54 and alsoextending radially therethrough. The openings defined by the inlets 68may include holes, slots, or a combination of holes and slots, forexample. An inner surface 55 of the wrapper 54 and the cooling channels56 on the downstream end portion 52 may form passages to receive an airflow provided via the inlets 68. By way of example, in one embodiment,each inlet 68 may supply an air flow (e.g., divert a portion of the airflowing upstream towards the fuel nozzles 12 through annular passages 36and 47) to a respective cooling channel 56 on the downstream end portion52. As the air (which is substantially cooler relative to thetemperature of the combustion gases within the combustion chamber 38)flows into and through the channels 56, heat is transferred away fromthe liner 34, thus cooling the liner 34. Additionally, as discussedabove, one or more of the channels 56 may include film holes fluidlycoupling the channel 56 to the combustion chamber 38. A portion of theair flow within the channel 56 may be diverted low through the filmholes to provide a cooling film that insulates the inner surface of theliner 34 from the combustion gases in the chamber 38. The liner 34 alsoincludes the bypass openings 41 which, as discussed above, may providean additional cooling film along the inner surface of the liner 34, thusproviding additional insulation for the liner 34.

FIG. 5 is a partial perspective view showing the cooling channels 56 onthe downstream end portion 52 of the liner 34 within the circular regiondefined by the arcuate line 5-5, as shown in FIG. 4. As shown in thedepicted embodiment, a plurality of axial cooling channels 56 arearranged circumferentially about the downstream end portion 52 of theliner 34. The channels 56 may define flow paths generally parallel toone another and the longitudinal axis 58 of the liner 34. In oneembodiment, the channels 56 may be formed by removing a portion of theouter surface of the downstream end portion 52, such that each coolingchannel 56 is a recessed groove between adjacent raised dividing members62. Thus, the cooling channels 56 may be defined by alternating axialgrooves and axial protrusions (e.g., 62) about a circumference of thecombustor liner 34. As will be appreciated, the channels 56 may beformed using any suitable technique, including milling, casting,molding, or laser etching/cutting, for example. The cooling channels 56,in one embodiment, may have an axial length (with respect to axis 58)that is substantially equivalent to the axial length L2 of thedownstream end portion 52, as discussed above. In other embodiments, thecooling channels 56 may have an axial length that is less than L2. Byway of example only, the axial length of each cooling channel 56 may beat least less than approximately 3, 4, 5, 6, 7, or 8 inches. In otherembodiments, however, the axial length of the cooling channels 56 may beless than 3 inches or greater than 8 inches. The cooling channels mayalso have various depths and widths. In one embodiment, the coolingchannels may have a width of at least less than approximately 0.25inches, 0.5 inches, 0.75 inches, or 1 inch. In other embodiments, thewidth may be less than 0.25 inches or greater than 1 inch. Further, inone embodiment, the depth of the cooling channels 56 may be at leastless than approximately 0.05 inches, 0.10 inches, 0.15 inches, 0.20inches, 0.25 inches, or 0.30 inches. In further embodiments, the depthof the cooling channels 56 may be less than 0.05 inches or greater than0.30 inches.

The film holes 64 extend radially through the axial grooves into aninterior of the combustor liner 34. In certain embodiments, the filmholes 64 may be arranged in a group, as shown in FIG. 5, at a particularaxial position along each cooling channel 56. For example, the filmholes 64 may include between approximately 1 and 20 or 1 and 10 openingsin a group, which may be disposed at an axial position of approximately20, 40, 60, or 80 percent of the length L2 of the cooling channel 56relative to the downstream end. In some embodiments, the film holes 64may be disposed at multiple axial positions, equally or non-equallyspaced relative to one another, along the length L2 of the channels 56.In the present figure, film holes 64 are shown in only one channel 56for purposes of simplicity. It should be appreciated that in an actualimplementation, similar arrangements of the illustrated film holes 64may be provided in more than one cooling channel 56 on the downstreamend portion 52 (e.g., each cooling channel 56 may include film holes 64in one or more locations).

As discussed above, the film holes 64 fluidly couple the channels 56 tothe combustion chamber 38 and may provide an insulating film of coolingair along the inner surface of the liner 34. In one embodiment, the filmholes 64 may have a diameter of at least less than approximately 0.01,0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.10 inches. In otherembodiments, the film holes 64 may be less than 0.01 inches or greaterthan 0.10 inches. FIG. 5 also shows the bypass openings 41 locatedupstream from the cooling channels 56. As discussed above, the bypassopenings 41 may provide a flow of air directly into the combustionchamber 38 (e.g., bypassing the cooling channels 56), thus providing anadditional cooling film along the inner surface of the liner 34, therebyfurther enhancing cooling of the liner 34. In one embodiment, the bypassopenings 41 may have dimensions similar to the film holes 64, asdiscussed above. That is, the bypass openings 41, in one embodiment, mayhave a diameter of at least less than approximately 0.01, 0.02, 0.03,0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.10 inches or, in otherembodiments, less than 0.01 inches or greater than 0.10 inches. As willbe appreciated, the presently illustrated embodiment is only intended byprovide an example of a particular implementation that utilizes both thefilm holes 64 and bypass openings 41 to cool the liner 34 via filmcooling and forced convection cooling. In another embodiment, the liner34 may include only the film holes 64 and not the bypass openings 41.

Referring now to FIG. 6, a partial cross-sectional side view of thecombustor 16 within the circular region defined by the arcuate line 6-6in FIG. 3 is illustrated. Particularly, FIG. 6 shows in more detail theair flow into the cooling channels 56 on downstream end portion 52 ofthe liner 34. Compressed air discharged by the compressor 24 may bereceived in the annular passage 47 (defined by the impingement sleeve 42and the transition piece 46) through the inlets 48. In the presentembodiment, the inlets 48 are circular-shaped holes, although in otherimplementations, the inlets 48 may be slots, or a combination of holesand slots of other geometries. As the air 72 within the annular passage47 is channeled upstream relative to the direction of the combustion gasflow (e.g., direction 39), the majority of the air 72 is discharged intothe annular passage 36 (defined by the flow sleeve 32 and the liner 34).As discussed above, the flow sleeve 32 may include the mounting flange44 at a downstream end 74 configured to receive a member 76 extendingradially outward from the upstream end 78 of the impingement sleeve 42,thereby fluidly coupling the flow sleeve 32 and impingement sleeve 42.In addition to receiving the air flow 72 from the annular passage 47,the annular passage 36 also receives a portion 80 of the compressed airfrom the plenum 31 by way of the inlets 40. That is, the airflow withinthe annular passage 36 may include air 72 discharged from the annularpassage 47 and air 80 flowing through the inlets 40. Thus, a flow paththat is directed upstream (with respect to the direction 39) is definedby the annular passages 36 and 47. Additionally, it should be understoodthat like the inlets 48 on the impingement sleeve 42, the inlets 40 mayalso include holes, slots, or a combination thereof, of various shapes.

While a majority of the air 72 flowing through the annular passage 47 isdischarged into the annular passage 36, a portion of the air flow, shownhere by the reference number 84, may be directed into the coolingchannels 56 on the downstream end portion 52 by way of a flow path Fprovided by the plurality of inlets 68 on the wrapper 54. The flow pathF may define an air flow through the cooling channels 56. As shown, theflow path F is directed downstream with respect to direction 39, and isopposite of the flow path through the annular passages 36 and 47. Thoughonly one cooling channel 56 is shown in the cross-sectional view of FIG.6, it should be understood that a similar air flow scheme may be appliedto each of the cooling channels 56 on the downstream end portion 52. Inone embodiment, the total air flow directed into and through the coolingchannels 56 about the downstream end portion 52 may represent at leastless than approximately 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 percent of thetotal compressed air supplied to the combustor 16. In other embodiments,the total air directed into the cooling channels 56 may be more than 10percent of the total compressed air supplied to the combustor 16.

As discussed above, the air 84 that flows into the depicted coolingchannel 56 is generally substantially cooler relative to the temperatureof the combustion gases within the combustion chamber 38. Thus, as theair 84 flows through the cooling channels 56 along the flow path F, heatmay be transferred away from the combustor liner 34, particularly thedownstream end portion 52 of the liner. By way of example, the mechanismemployed in cooling the liner 34 may be forced convective heat transferresulting from the contact between the cooling air 84 and the outersurface of downstream end portion 52, which may include the grooves anddividing members 62 defining the channels 56, as discussed above withreference to FIG. 5. The flow path F may continue along the axial lengthof the cooling channel 56, wherein the cooling air 84 exits the coolingchannel 56 at a downstream end (not shown), thereby discharging into thetransition piece cavity 50, whereby the cooling air 84 is directedtowards combustion gases flowing downstream (away from the fuel nozzles12) through the transition piece cavity 50.

As shown in the present embodiment, a portion 53 of the cooling air 84may flow through the film holes 64 within the cooling channel 56 andinto the combustion chamber 38. The air 53 may provide a cooling film 86that insulates the liner 34 from the combustion gases within the chamber38, as discussed above. The depicted cooling film 86 may also includethe air flow 43, which may be provided through the bypass openings 41 onthe liner 34. Thus, air directed through the film holes 64 and thebypass openings 41 may both contribute to the formation of the coolingfilm 86.

Referring now to FIGS. 7A and 7B, cross-sectional end views of thecooling channel 56 with respect to the cut line 7-7 of FIG. 6 areillustrated in accordance with embodiments of the invention. Referringfirst to FIG. 7A, the transition piece 46, seal 66, wrapper 54, anddownstream end portion 52 of the liner 34 are shown in the arrangementdescribed above. As discussed, the cooling channels 56 may be formed byremoving a portion of the liner 34 to define a groove between dividingmembers 62. In the illustrated embodiment, the dividing members 62 mayhave a height 94 of approximately at least less than approximately 0.05inches, 0.10 inches, 0.15 inches, 0.20 inches, 0.25 inches, or 0.30inches, which may corresponding to the depth of the cooling channel 56,as mentioned above. In further embodiments, the height 94 of thedividing members 62 may be less than 0.05 inches or greater than 0.30inches. Additionally, the width 90 of the cooling channel 56 may bedefined as a circumferential distance between the sidewalls 92 of twoadjacent dividing members 62. As discussed above, in one embodiment, thewidth 90 (e.g., circumferential width) of each cooling channel 56 may beat least less than approximately 0.25 inches, 0.5 inches, 0.75 inches,or 1 inch. In other embodiments, the width 90 may be less than 0.25inches or greater than 1 inch.

In the depicted embodiment, the cooling channel 56 may have asubstantially flat and/or smooth surface 95. For example, the surface 95may be flat in the axial and/or circumferential directions, or thesurface 95 may have a slight curvature in the circumferential directiondue to the annular shape of the liner 34. By further example, thesurface 95 may be substantially or entirely free of protrusions,recesses, or surface texture except for the film holes 64. As coolingair (e.g., air 84) flows through the channel 56 in the downstreamdirection 39 (i.e., perpendicular to the page) and contacts the surface95 and sidewalls 92, heat may be transferred away from the liner 34,particularly the downstream end portion 52 of the liner 34, via forcedconvection cooling. Additionally, as mentioned above, a portion 53 ofthe cooling air 84 may flow through one or more film holes 64 thatextend radially through the channel 56 and fluidly couple the channel 56to the combustion chamber 38. As the air 53 flows through the film holes64 and into the chamber 38, a cooling film 86 is formed. As discussedabove, the cooling film 86 may insulate the liner 34 from the hotcombustion gases within the chamber 38.

While the present view depicted by FIG. 7A shows three film holes 64distributed circumferentially across the width 90 of the cooling channel56, it should be understood that this is meant to provide merely oneexample of how the film holes 64 may be arranged within the channel 56.Indeed, any other suitable arrangement of film holes 64 may be employed.For instance, a plurality of film holes 64 may be arranged in bothcircumferential and axial directions within the cooling channel 56.Further, as will be discussed further below with respect to FIG. 9, insome embodiments, the film holes 64 may be arranged in a plurality ofgroups axially spaced along the axial length of the cooling channel 56.

Referring to FIG. 7B, an alternate embodiment of the cooling channel 56is illustrated. In contrast to the flat and/or smooth surface 95 shownin FIG. 7A, the surface 95 of the embodiment depicted in FIG. 7B mayinclude a plurality of surface features 96, which may be discreteprotrusions extending from the surface 95. By way of example, thesurface features may include fin-shaped protrusions, cylindrical-shapedprotrusions, ring-shaped protrusions, chevron-shaped protrusions, raisedportions between cross-hatched grooves formed with in the coolingchannel 56, or some combination thereof, as well as any other type ofsuitable geometric shape. It should be appreciated that the dimensionsof the surface features 96 may be selected to optimize cooling whilesatisfying the geometric constraints of the cooling channels 56 (e.g.,based upon the cooling channel dimensions discussed above).

The surface features 96 may further enhance the forced convectivecooling of the liner 34 by increasing the surface area of the downstreamend portion 52 via which the cooling air 84 may contact as it flowsthrough the channel 56. Thus, in the present embodiment, as the air 84flows through the channel 56 and contacts the surface features 96, theamount of heat transferred away from the liner 34 may be greaterrelative to the embodiment shown in FIG. 7A, in which the coolingchannel 56 has a substantially flat and/or smooth surface 95. Further,while the presently illustrated embodiments show surface features 96formed only on the surface 95, in other embodiments, the surfacefeatures 96 may also be formed on the sidewalls 92 of the channel 56.

Continuing now to FIGS. 8A-8D, cross-sectional side views of the coolingchannel 56 within the circular region defined by the arcuate line 8-8 inFIG. 6 is illustrated. Particularly, FIGS. 8A-8D illustrate severalshapes in which the film holes 64 may be formed, in accordance withembodiments of the present invention. For instance, referring to theembodiment shown in FIG. 8A, a film hole 64 extending through thedownstream end portion 52 within the cooling channel 56 may includeedges 104 that are parallel to each other and perpendicular to thelongitudinal axis 58 of the liner 34. In other words, the edges 104 ofthe film hole 64 may define a straight cylindrical passage with an angleof approximately 90 degrees relative to the inner and outer surfaces ofthe liner 34. Thus, the outer opening 100 (adjacent to the coolingchannel 56) and the inner opening 102 (adjacent to the combustionchamber 38) are substantially equal in size. As described above, thefilm hole 64 may provide a path through which a portion 53 of coolingair 84 flowing through the channel 56 may flow directly into thecombustion chamber 38 to provide an insulting cooling film 86.

FIG. 8B shows an alternate embodiment of the film hole 64 in which theedges 104 are parallel to each other, but are angled with respect to thelongitudinal axis 58 of the liner 34. In other words, the edges 104 ofthe film hole 64 may define a straight cylindrical passage with an anglebetween approximately 0 and 90 degrees, 30 and 60 degrees, or about 45degrees relative to the inner and outer surfaces of the liner 34. Thus,the outer opening 100 and the inner opening 102 are also substantiallyequal in size, but the path through which the portion of air 53 flowsinto the combustion chamber 38 may be angled based upon the angle of theedges 104.

FIG. 8C shows a further embodiment in which the film hole 64 is tapered,such that the outer opening 100 is smaller relative to the inner opening102. In other words, the edges 104 of the film hole 64 may define adiverging passage, e.g., generally conical shaped, from the innersurface (e.g., along cooling channel 56) to the outer surface (e.g., incombustion chamber 38). Furthermore, a centerline of the film hole 64may have an angle between approximately 0 and 90 degrees, 30 and 60degrees, or about 45 or 90 degrees relative to the inner and outersurfaces of the liner 34.

FIG. 8D shows yet another embodiment in which the film hole 64 istapered, such that the outer opening 100 is larger relative to the inneropening 102. In other words, the edges 104 of the film hole 64 maydefine a converging passage, e.g., generally conical shaped, from theinner surface (e.g., along cooling channel 56) to the outer surface(e.g., in combustion chamber 38). Furthermore, a centerline of the filmhole 64 may have an angle between approximately 0 and 90 degrees, 30 and60 degrees, or about 45 or 90 degrees relative to the inner and outersurfaces of the liner 34.

As mentioned above, the diameters of the film holes 64 may be at leastless than approximately 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08,0.09, or 0.10 inches. In other embodiments, the film holes 64 may beless than 0.01 inches or greater than 0.10 inches. Further, while thefilm holes 64 depicted in FIGS. 8A-8D are shown as being generallycircular in shape, it should be appreciated that in other embodiments,the film holes 62 may be square-shaped, rectangular shaped, oval-shaped,or any other type of suitable geometric shape, and may be formed usingany suitable technique, such as laser drilling. Still further, it shouldbe understood that the various embodiments of the film holes 64 depictedherein may be similarly applied in forming the bypass openings 41located upstream from the downstream end portion 52.

FIG. 9 shows a partial cross-sectional side view of the combustor 16within the circular region defined by the arcuate line 6-6 in FIG. 3, inaccordance with a further embodiment of the invention. Particularly,FIG. 9 depicts an embodiment in which a plurality of sets of film holes64 are provided and axially spaced along the axial length of the coolingchannel 56. For instance, in the illustrated embodiment, the channel 56may include a first set of film holes 64 a, a second set of film holes64 b located downstream from the first set 64 a, and a third set of filmholes 64 c located downstream from the second set 64 b. Thus, as thecooling air 84 flows into the cooling channel 56 by way of the inlets 68on the wrapper 54, portions 53 of the cooling air 84 may flow througheach set of film holes 64 a, 64 b, and 64 c in series. As will beappreciated, this arrangement may not only increases the amount of air53 supplied to the combustion chamber 38, but also distribute the air 53more evenly across the inner surface of the downstream end portion 52,thus providing a more uniform cooling film 86 for insulating the liner34.

Additionally, FIG. 9 also illustrates the use of multiple sets of bypassopenings 41. For instance, referring back to the embodiment shown inFIGS. 4 and 5, a single set of bypass openings 41 disposedcircumferentially about the liner 34 is illustrated. In FIG. 9, threesuch sets of axially spaced bypass openings, referred to here byreference numbers 41 a, 41 b, and 41 c, may be utilized in cooling theliner 34. That is, each of the bypass openings shown in thecross-sectional view of FIG. 9 may correspond to a respective set ofbypass openings arranged circumferentially about the liner 34. A portionof air 43 from the annular passage 36 may flow into each of the bypassopenings 41 a, 41 b, and 41 c into the combustion chamber 38. Asdiscussed above, this air flow 43 may provide an additional coolingfilm, or may contribute to the cooling film 86 that is supplied via theair flow 53 through the film holes 64 a, 64 b, and 64 c. As will beappreciated, the use of multiple sets of bypass openings 41 a, 41 b, and41 c may further increase the area and uniformity of the cooling film86, thus further improving the insulation of the liner 34 from thecombustion gases within the chamber 38.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

1. A system comprising: a turbine engine comprising: a combustorcomprising a hollow wall having a sleeve disposed about a combustorliner, wherein the combustor liner comprises an inner surface facinginwardly toward a combustion chamber; a first air flow path in anupstream direction through the hollow wall toward a head end of thecombustor, wherein the first air flow path comprises a plurality ofbypass openings extending through the combustor liner to the innersurface, wherein the plurality of bypass openings is configured tosupply a first cooling film to a downstream end portion of the combustorliner; and a second air flow path in a downstream direction opposite theupstream direction through the hollow wall, wherein the second flow pathcomprises a plurality of film holes extending through the combustorliner to the inner surface, and the plurality of film holes isconfigured to supply a second cooling film to the downstream end portionof the combustor liner downstream of the first cooling film.
 2. Thesystem of claim 1, wherein the plurality of bypass openings extendingthrough the combustor liner is disposed upstream of the plurality offilm holes extending through the combustor liner.
 3. The system of claim2, wherein the plurality of bypass openings extend through thedownstream end portion of the combustor liner, and an axial length ofthe downstream end portion is less than or equal to approximately 35percent of a total axial length of the combustor liner.
 4. The system ofclaim 1, wherein the second air flow path is defined by a passage formedby an axial cooling channel on the downstream end portion of thecombustor liner and an inner surface of a wrapper coaxially disposedgenerally about the downstream end portion.
 5. The system of claim 4,wherein the wrapper comprises one or more radial openings configured tosupply a portion of an air flow along the first air flow path into theaxial cooling channel.
 6. The system of claim 5, wherein the pluralityof film holes extends radially through the axial cooling channeldownstream of the one or more radial openings, and the plurality of filmholes is configured to direct the portion of the air flow to supply thesecond cooling film to the downstream end portion of the combustorliner.
 7. The system of claim 1, wherein the first air flow path is atleast partially defined by a first passage between a transition pieceand a transition sleeve that surrounds the transition piece.
 8. Thesystem of claim 7, wherein the first passage is fluidly coupled to asecond passage between the combustor liner and the transition sleeve,wherein the second passage extends in the upstream direction from thefirst passage, the first passage comprises a first plurality of inletsto receive a first portion of air that flows through the first passageand the second passage in the upstream direction, and the second passagecomprises a second plurality of inlets to receive a second portion ofair that flows through the second passage in the upstream direction. 9.The system of claim 8, wherein the turbine engine comprises one or morefuel nozzles, wherein the fuel nozzles are configured to receive thefirst portion of air and the second portion of air flowing in theupstream direction through the second passage and to mix the firstportion of air and the second portion of air with a fuel, and whereinthe fuel nozzles are configured to output a resulting air-fuel mixtureinto the combustion chamber surrounded by the combustor liner forcombustion.
 10. A system comprising: a turbine combustor linercomprising: a plurality of axial cooling channels arrangedcircumferentially about a downstream end portion relative to adownstream direction of combustion along a longitudinal axis of theturbine combustor liner; an inner surface facing inwardly toward acombustion chamber; and a plurality of bypass openings arrangedcircumferentially about the downstream end portion upstream of theplurality of axial cooling channels, wherein the plurality of bypassopenings is configured to supply a first cooling film to the innersurface of the combustor liner, and each of the plurality of axialcooling channels comprises a plurality of film holes configured tosupply a second cooling film to the inner surface of the combustor linerat the downstream end portion.
 11. The system of claim 10, wherein aninterior of the turbine combustor liner has a combustion path with adownstream direction of flow of combustion gases, an exterior of theturbine combustor liner has a first air path with an upstream directionof flow opposite to the downstream direction, and the exterior of theturbine combustor liner has the plurality of cooling channels with asecond air path in the downstream direction.
 12. The system of claim 11,comprising a first flow sleeve disposed about the turbine combustorliner to define a first hollow wall, and a second flow sleeve disposedabout a transition piece to define a second hollow wall, wherein thefirst and second hollow walls are coupled to one another at thedownstream end portion, the first and second hollow walls define thefirst air path with the upstream direction, and the second air path inthe downstream direction is disposed radially between the plurality ofcooling channels and the transition piece.
 13. The system of claim 10,wherein the plurality of cooling channels is defined by alternatingaxial grooves and axial protrusions about a circumference of the turbinecombustor liner, and the plurality of film holes extend radially throughthe axial grooves into an interior of the turbine combustor liner. 14.The system of claim 10, wherein the plurality of bypass openings extendradially through the combustor liner at an angle of approximately 90degrees relative to the inner surface.
 15. The system of claim 10,wherein the plurality of bypass openings extend radially through thecombustor liner at an angle between approximately 30 to 60 degrees. 16.The system of claim 10, wherein at least one bypass opening of theplurality of bypass openings has a geometry that converges or divergesthrough the combustor liner into the interior of the turbine combustorliner.
 17. The system of claim 10, wherein each bypass opening of theplurality of bypass openings is disposed in an upstream direction ofcombustion along the longitudinal axis from an axial cooling channel ofthe plurality of axial cooling channels.
 18. The system of claim 10,wherein the bypass openings are arranged in two or more axially spacedsets, wherein each set is disposed circumferentially about thedownstream end portion.
 19. The system of claim 10, wherein an axiallength of the downstream end portion is less than or equal toapproximately 35 percent of a total axial length of the turbinecombustor liner, an axial channel length of each of the plurality ofcooling channels is less than or equal to the axial length of thedownstream end portion, and the cooling channels have a depth ofapproximately 0.05 to 0.30 inches and a width of approximately 0.25 to1.0 inches.
 20. A system comprising: a turbine engine comprising: acombustor comprising: a flow sleeve; and a combustor liner surrounded bythe flow sleeve and defining a flow path therebetween configured toreceive an air flow in a first direction toward a head end chamber,wherein the combustor liner comprises: an inner surface facing inwardlytoward a combustion chamber; a plurality of axial cooling channelsarranged circumferentially about a downstream end portion of thecombustor liner; a plurality of bypass holes arranged in two or moreaxially spaced sets at the downstream end portion, wherein each bypassopening is disposed upstream in the first direction relative to an axialcooling channel of the plurality of axial cooling channels, and eachbypass opening is configured to supply a first cooling film to the innersurface of the combustor liner at the downstream end portion; one ormore fuel nozzles disposed in the head end chamber of the combustor; andwherein each of the plurality of axial cooling channels comprises aplurality of film holes extending through the combustor liner to theinner surface, each of the plurality of axial cooling channels isconfigured to receive a portion of the air flow from the flow path, todirect a first portion of the received air along an axial length of theaxial cooling channel in a second direction away from the head endchamber, and to direct a second portion of the received air through theplurality of film holes to supply a second cooling film to the innersurface of the combustor liner at the downstream end portion.